Most people think of swimming pools when they hear the word chlorine. But this element does a whole lotmore: Two out of every three chemical products require chlorine in their manufacture. Numerous products such as medicines, plastics, textile fibres and dyes are only made possible thanks to this. Unfortunately, up until now chlorine production has required a significant amount of energy and is therefore climate-relevant. Bayer MaterialScience has developed a technology together with partners, that decreases the amount of energy needed by up to 30 per cent in comparison with the standard procedure.

More energy is required to manufacture chlorine than almost any other chemical product: Three per cent of the total electricity requirement in Germany per year is due to the manufacture of approximately 4.5 million tonnes of chlorine alone. Bayer MaterialScience has developed an energy-saving process for chlorine production, which would reduce the demand for electricity in the Federal Republic by around one per cent – if it were applied across the board. This corresponds to the annual demand for electricity of a city such as Cologne and saving of approximately two million tonnes of CO2 emissions.

Engine for progress:

• savings of 10,000 tonnes of CO2 per year by the demo plant alone• 30 per cent electricity savings in chlorine production• no need for expensive precious metal catalysts• recycling of the silver used• existing plants can be retrofitted

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Photo: Bayer MaterialScience

At the demonstration plant in Uerdingen, 20,000 tonnes of chlorine can already be produced per year with the new technology from Bayer MaterialScience.

New electrodes reduce the voltage and the electricity consumption

The core of the process is the use of a novel electrode, the "oxygen depolarised cathode", or ODC for short. Chlorine is produced through the electrolysis of a sodium chloride solution. By applying a voltage to the saline solution, chlorine gas is formed in one electrode and hydrogen in the other. Using the new method, hydrogen formation is prevented through targeted oxygen supply, so that the voltage is reduced and 30 per cent less electricity is required. "The ODC technology offers great ecological and economical utility, because it can make an important contribution to increasing energy efficiency and therefore to climate protection in Germany too," explains Dr. Klaus Schäfer, member of the Executive Committee at Bayer MaterialScience and Director of the Industrial Operations Division. A further advantage of this method: The new electrode no longer contains expensive precious metals, such as ruthenium for example. Silver is used of course, but this can be recycled – thanks to another newly developed procedure.

Demonstration plant already saves 10,000 tonnes of CO2

The new process has already been successfully implemented by Bayer MaterialScience at a demonstration plant at Chemiepark Krefeld-Uerdingen: 20,000 tonnes of chlorine can be produced here annually using the oxygen depolarised cathode. The demo production alone is already saving approximately 10,000 tonnes of CO2 per year.In fact, the principle of the method is already well known from the field of fuel cell technology. However, transferring this technology to chlorine production failed before now on the basis of the provision of materials with greater performance and long-term stability. Bayer MaterialScience had been working on the development for 20 years – then came the breakthrough. Together with the development partner, ThyssenKrupp Electrolysis, the technology has been available worldwide since 2013.Now, even the field of application has expanded: Further possible uses are arising, for example in the areas of stationary energy storage or the treatment of drinking water.

Energy-saving chlorine production project video

Video: KlimaExpo.NRW

Photo: Covestro

"The ODC process has the potential to contribute to the success of German technologies on the world market."

Dr. Klaus Schäfer, member of the Executive Committee at Bayer MaterialScience and Director of the Industrial Operations Division